| // Copyright (c) 2017 The Khronos Group Inc. |
| // Copyright (c) 2017 Valve Corporation |
| // Copyright (c) 2017 LunarG Inc. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| #include "aggressive_dead_code_elim_pass.h" |
| |
| #include "cfa.h" |
| #include "iterator.h" |
| #include "latest_version_glsl_std_450_header.h" |
| |
| #include <stack> |
| |
| namespace spvtools { |
| namespace opt { |
| |
| namespace { |
| |
| const uint32_t kTypePointerStorageClassInIdx = 0; |
| const uint32_t kEntryPointFunctionIdInIdx = 1; |
| const uint32_t kSelectionMergeMergeBlockIdInIdx = 0; |
| const uint32_t kLoopMergeMergeBlockIdInIdx = 0; |
| const uint32_t kLoopMergeContinueBlockIdInIdx = 1; |
| |
| } // namespace |
| |
| bool AggressiveDCEPass::IsVarOfStorage(uint32_t varId, uint32_t storageClass) { |
| if (varId == 0) return false; |
| const ir::Instruction* varInst = get_def_use_mgr()->GetDef(varId); |
| const SpvOp op = varInst->opcode(); |
| if (op != SpvOpVariable) return false; |
| const uint32_t varTypeId = varInst->type_id(); |
| const ir::Instruction* varTypeInst = get_def_use_mgr()->GetDef(varTypeId); |
| if (varTypeInst->opcode() != SpvOpTypePointer) return false; |
| return varTypeInst->GetSingleWordInOperand(kTypePointerStorageClassInIdx) == |
| storageClass; |
| } |
| |
| bool AggressiveDCEPass::IsLocalVar(uint32_t varId) { |
| return IsVarOfStorage(varId, SpvStorageClassFunction) || |
| (IsVarOfStorage(varId, SpvStorageClassPrivate) && private_like_local_); |
| } |
| |
| void AggressiveDCEPass::AddStores(uint32_t ptrId) { |
| get_def_use_mgr()->ForEachUser(ptrId, [this](ir::Instruction* user) { |
| switch (user->opcode()) { |
| case SpvOpAccessChain: |
| case SpvOpInBoundsAccessChain: |
| case SpvOpCopyObject: |
| this->AddStores(user->result_id()); |
| break; |
| case SpvOpLoad: |
| break; |
| // If default, assume it stores e.g. frexp, modf, function call |
| case SpvOpStore: |
| default: |
| if (!IsLive(user)) AddToWorklist(user); |
| break; |
| } |
| }); |
| } |
| |
| bool AggressiveDCEPass::AllExtensionsSupported() const { |
| // If any extension not in whitelist, return false |
| for (auto& ei : get_module()->extensions()) { |
| const char* extName = |
| reinterpret_cast<const char*>(&ei.GetInOperand(0).words[0]); |
| if (extensions_whitelist_.find(extName) == extensions_whitelist_.end()) |
| return false; |
| } |
| return true; |
| } |
| |
| bool AggressiveDCEPass::IsTargetDead(ir::Instruction* inst) { |
| const uint32_t tId = inst->GetSingleWordInOperand(0); |
| const ir::Instruction* tInst = get_def_use_mgr()->GetDef(tId); |
| if (dead_insts_.find(tInst) != dead_insts_.end()) { |
| return true; |
| } |
| return false; |
| } |
| |
| void AggressiveDCEPass::ProcessLoad(uint32_t varId) { |
| // Only process locals |
| if (!IsLocalVar(varId)) return; |
| // Return if already processed |
| if (live_local_vars_.find(varId) != live_local_vars_.end()) return; |
| // Mark all stores to varId as live |
| AddStores(varId); |
| // Cache varId as processed |
| live_local_vars_.insert(varId); |
| } |
| |
| bool AggressiveDCEPass::IsStructuredIfOrLoopHeader(ir::BasicBlock* bp, |
| ir::Instruction** mergeInst, |
| ir::Instruction** branchInst, |
| uint32_t* mergeBlockId) { |
| ir::Instruction* mi = bp->GetMergeInst(); |
| if (mi == nullptr) return false; |
| ir::Instruction* bri = &*bp->tail(); |
| // Make sure it is not a Switch |
| if (mi->opcode() == SpvOpSelectionMerge && |
| bri->opcode() != SpvOpBranchConditional) |
| return false; |
| if (branchInst != nullptr) *branchInst = bri; |
| if (mergeInst != nullptr) *mergeInst = mi; |
| if (mergeBlockId != nullptr) *mergeBlockId = mi->GetSingleWordInOperand(0); |
| return true; |
| } |
| |
| void AggressiveDCEPass::ComputeBlock2HeaderMaps( |
| std::list<ir::BasicBlock*>& structuredOrder) { |
| block2headerBranch_.clear(); |
| branch2merge_.clear(); |
| std::stack<ir::Instruction*> currentHeaderBranch; |
| currentHeaderBranch.push(nullptr); |
| uint32_t currentMergeBlockId = 0; |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| // If this block is the merge block of the current control construct, |
| // we are leaving the current construct so we must update state |
| if ((*bi)->id() == currentMergeBlockId) { |
| currentHeaderBranch.pop(); |
| ir::Instruction* chb = currentHeaderBranch.top(); |
| if (chb != nullptr) |
| currentMergeBlockId = branch2merge_[chb]->GetSingleWordInOperand(0); |
| } |
| ir::Instruction* mergeInst; |
| ir::Instruction* branchInst; |
| uint32_t mergeBlockId; |
| bool is_header = |
| IsStructuredIfOrLoopHeader(*bi, &mergeInst, &branchInst, &mergeBlockId); |
| // If this is a loop header, update state first so the block will map to |
| // the loop. |
| if (is_header && mergeInst->opcode() == SpvOpLoopMerge) { |
| currentHeaderBranch.push(branchInst); |
| branch2merge_[branchInst] = mergeInst; |
| currentMergeBlockId = mergeBlockId; |
| } |
| // Map the block to the current construct. |
| block2headerBranch_[*bi] = currentHeaderBranch.top(); |
| // If this is an if header, update state so following blocks map to the if. |
| if (is_header && mergeInst->opcode() == SpvOpSelectionMerge) { |
| currentHeaderBranch.push(branchInst); |
| branch2merge_[branchInst] = mergeInst; |
| currentMergeBlockId = mergeBlockId; |
| } |
| } |
| } |
| |
| void AggressiveDCEPass::ComputeInst2BlockMap(ir::Function* func) { |
| for (auto& blk : *func) { |
| blk.ForEachInst( |
| [&blk, this](ir::Instruction* ip) { inst2block_[ip] = &blk; }); |
| } |
| } |
| |
| void AggressiveDCEPass::AddBranch(uint32_t labelId, ir::BasicBlock* bp) { |
| std::unique_ptr<ir::Instruction> newBranch(new ir::Instruction( |
| context(), SpvOpBranch, 0, 0, |
| {{spv_operand_type_t::SPV_OPERAND_TYPE_ID, {labelId}}})); |
| get_def_use_mgr()->AnalyzeInstDefUse(&*newBranch); |
| bp->AddInstruction(std::move(newBranch)); |
| } |
| |
| void AggressiveDCEPass::AddBreaksAndContinuesToWorklist( |
| ir::Instruction* loopMerge) { |
| const uint32_t mergeId = |
| loopMerge->GetSingleWordInOperand(kLoopMergeMergeBlockIdInIdx); |
| get_def_use_mgr()->ForEachUser( |
| mergeId, [&loopMerge, this](ir::Instruction* user) { |
| // A branch to the merge block can only be a break if it is nested in |
| // the current loop |
| SpvOp op = user->opcode(); |
| if (op != SpvOpBranchConditional && op != SpvOpBranch) return; |
| ir::Instruction* branchInst = user; |
| while (true) { |
| ir::BasicBlock* blk = inst2block_[branchInst]; |
| ir::Instruction* hdrBranch = block2headerBranch_[blk]; |
| if (hdrBranch == nullptr) return; |
| ir::Instruction* hdrMerge = branch2merge_[hdrBranch]; |
| if (hdrMerge == loopMerge) break; |
| branchInst = hdrBranch; |
| } |
| if (!IsLive(user)) { |
| AddToWorklist(user); |
| // Add branch's merge if there is one |
| ir::Instruction* userMerge = branch2merge_[user]; |
| if (userMerge != nullptr) AddToWorklist(userMerge); |
| } |
| }); |
| const uint32_t contId = |
| loopMerge->GetSingleWordInOperand(kLoopMergeContinueBlockIdInIdx); |
| get_def_use_mgr()->ForEachUser(contId, [&contId, |
| this](ir::Instruction* user) { |
| SpvOp op = user->opcode(); |
| if (op == SpvOpBranchConditional) { |
| // A conditional branch can only be a continue if it does not have a merge |
| // instruction or its merge block is not the continue block. |
| ir::Instruction* hdrMerge = branch2merge_[user]; |
| if (hdrMerge != nullptr && hdrMerge->opcode() == SpvOpSelectionMerge) { |
| uint32_t hdrMergeId = |
| hdrMerge->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx); |
| if (hdrMergeId == contId) return; |
| // Need to mark merge instruction too |
| if (!IsLive(hdrMerge)) AddToWorklist(hdrMerge); |
| } |
| } else if (op == SpvOpBranch) { |
| // An unconditional branch can only be a continue if it is not |
| // branching to its own merge block. |
| ir::BasicBlock* blk = inst2block_[user]; |
| ir::Instruction* hdrBranch = block2headerBranch_[blk]; |
| if (hdrBranch == nullptr) return; |
| ir::Instruction* hdrMerge = branch2merge_[hdrBranch]; |
| if (hdrMerge->opcode() == SpvOpLoopMerge) return; |
| uint32_t hdrMergeId = |
| hdrMerge->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx); |
| if (contId == hdrMergeId) return; |
| } else { |
| return; |
| } |
| if (!IsLive(user)) AddToWorklist(user); |
| }); |
| } |
| |
| bool AggressiveDCEPass::AggressiveDCE(ir::Function* func) { |
| // Compute map from instruction to block |
| ComputeInst2BlockMap(func); |
| // Compute map from block to controlling conditional branch |
| std::list<ir::BasicBlock*> structuredOrder; |
| cfg()->ComputeStructuredOrder(func, &*func->begin(), &structuredOrder); |
| ComputeBlock2HeaderMaps(structuredOrder); |
| bool modified = false; |
| // Add instructions with external side effects to worklist. Also add branches |
| // EXCEPT those immediately contained in an "if" selection construct or a loop |
| // or continue construct. |
| // TODO(greg-lunarg): Handle Frexp, Modf more optimally |
| call_in_func_ = false; |
| func_is_entry_point_ = false; |
| private_stores_.clear(); |
| // Stacks to keep track of when we are inside an if- or loop-construct. |
| // When immediately inside an if- or loop-construct, we do not initially |
| // mark branches live. All other branches must be marked live. |
| std::stack<bool> assume_branches_live; |
| std::stack<uint32_t> currentMergeBlockId; |
| // Push sentinel values on stack for when outside of any control flow. |
| assume_branches_live.push(true); |
| currentMergeBlockId.push(0); |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| // If exiting if or loop, update stacks |
| if ((*bi)->id() == currentMergeBlockId.top()) { |
| assume_branches_live.pop(); |
| currentMergeBlockId.pop(); |
| } |
| for (auto ii = (*bi)->begin(); ii != (*bi)->end(); ++ii) { |
| SpvOp op = ii->opcode(); |
| switch (op) { |
| case SpvOpStore: { |
| uint32_t varId; |
| (void)GetPtr(&*ii, &varId); |
| // Mark stores as live if their variable is not function scope |
| // and is not private scope. Remember private stores for possible |
| // later inclusion |
| if (IsVarOfStorage(varId, SpvStorageClassPrivate)) |
| private_stores_.push_back(&*ii); |
| else if (!IsVarOfStorage(varId, SpvStorageClassFunction)) |
| AddToWorklist(&*ii); |
| } break; |
| case SpvOpLoopMerge: { |
| assume_branches_live.push(false); |
| currentMergeBlockId.push( |
| ii->GetSingleWordInOperand(kLoopMergeMergeBlockIdInIdx)); |
| } break; |
| case SpvOpSelectionMerge: { |
| auto brii = ii; |
| ++brii; |
| bool is_structured_if = brii->opcode() == SpvOpBranchConditional; |
| assume_branches_live.push(!is_structured_if); |
| currentMergeBlockId.push( |
| ii->GetSingleWordInOperand(kSelectionMergeMergeBlockIdInIdx)); |
| if (!is_structured_if) AddToWorklist(&*ii); |
| } break; |
| case SpvOpBranch: |
| case SpvOpBranchConditional: { |
| if (assume_branches_live.top()) AddToWorklist(&*ii); |
| } break; |
| default: { |
| // Function calls, atomics, function params, function returns, etc. |
| // TODO(greg-lunarg): function calls live only if write to non-local |
| if (!context()->IsCombinatorInstruction(&*ii)) { |
| AddToWorklist(&*ii); |
| } |
| // Remember function calls |
| if (op == SpvOpFunctionCall) call_in_func_ = true; |
| } break; |
| } |
| } |
| } |
| // See if current function is an entry point |
| for (auto& ei : get_module()->entry_points()) { |
| if (ei.GetSingleWordInOperand(kEntryPointFunctionIdInIdx) == |
| func->result_id()) { |
| func_is_entry_point_ = true; |
| break; |
| } |
| } |
| // If the current function is an entry point and has no function calls, |
| // we can optimize private variables as locals |
| private_like_local_ = func_is_entry_point_ && !call_in_func_; |
| // If privates are not like local, add their stores to worklist |
| if (!private_like_local_) |
| for (auto& ps : private_stores_) AddToWorklist(ps); |
| // Add OpGroupDecorates to worklist because they are a pain to remove |
| // ids from. |
| // TODO(greg-lunarg): Handle dead ids in OpGroupDecorate |
| for (auto& ai : get_module()->annotations()) { |
| if (ai.opcode() == SpvOpGroupDecorate) AddToWorklist(&ai); |
| } |
| // Perform closure on live instruction set. |
| while (!worklist_.empty()) { |
| ir::Instruction* liveInst = worklist_.front(); |
| // Add all operand instructions if not already live |
| liveInst->ForEachInId([&liveInst, this](const uint32_t* iid) { |
| ir::Instruction* inInst = get_def_use_mgr()->GetDef(*iid); |
| // Do not add label if an operand of a branch. This is not needed |
| // as part of live code discovery and can create false live code, |
| // for example, the branch to a header of a loop. |
| if (inInst->opcode() == SpvOpLabel && liveInst->IsBranch()) return; |
| if (!IsLive(inInst)) AddToWorklist(inInst); |
| }); |
| // If in a structured if or loop construct, add the controlling |
| // conditional branch and its merge. Any containing control construct |
| // is marked live when the merge and branch are processed out of the |
| // worklist. |
| ir::BasicBlock* blk = inst2block_[liveInst]; |
| ir::Instruction* branchInst = block2headerBranch_[blk]; |
| if (branchInst != nullptr && !IsLive(branchInst)) { |
| AddToWorklist(branchInst); |
| ir::Instruction* mergeInst = branch2merge_[branchInst]; |
| AddToWorklist(mergeInst); |
| // If in a loop, mark all its break and continue instructions live |
| if (mergeInst->opcode() == SpvOpLoopMerge) |
| AddBreaksAndContinuesToWorklist(mergeInst); |
| } |
| // If local load, add all variable's stores if variable not already live |
| if (liveInst->opcode() == SpvOpLoad) { |
| uint32_t varId; |
| (void)GetPtr(liveInst, &varId); |
| if (varId != 0) { |
| ProcessLoad(varId); |
| } |
| } |
| // If function call, treat as if it loads from all pointer arguments |
| else if (liveInst->opcode() == SpvOpFunctionCall) { |
| liveInst->ForEachInId([this](const uint32_t* iid) { |
| // Skip non-ptr args |
| if (!IsPtr(*iid)) return; |
| uint32_t varId; |
| (void)GetPtr(*iid, &varId); |
| ProcessLoad(varId); |
| }); |
| } |
| // If function parameter, treat as if it's result id is loaded from |
| else if (liveInst->opcode() == SpvOpFunctionParameter) { |
| ProcessLoad(liveInst->result_id()); |
| } |
| worklist_.pop(); |
| } |
| // Mark all non-live instructions dead except non-structured branches, which |
| // now should be considered live unless their block is deleted. |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end(); ++bi) { |
| for (auto ii = (*bi)->begin(); ii != (*bi)->end(); ++ii) { |
| if (IsLive(&*ii)) continue; |
| // TODO(greg-lunarg |
| // https://github.com/KhronosGroup/SPIRV-Tools/issues/1021) This should be |
| // using ii->IsBranch(), but this code does not handle OpSwitch |
| // instructions yet. |
| if ((ii->opcode() == SpvOpBranch || |
| ii->opcode() == SpvOpBranchConditional) && |
| !IsStructuredIfOrLoopHeader(*bi, nullptr, nullptr, nullptr)) |
| continue; |
| dead_insts_.insert(&*ii); |
| } |
| } |
| // Remove debug and annotation statements referencing dead instructions. |
| // This must be done before killing the instructions, otherwise there are |
| // dead objects in the def/use database. |
| ir::Instruction* instruction = &*get_module()->debug2_begin(); |
| while (instruction) { |
| if (instruction->opcode() != SpvOpName) { |
| instruction = instruction->NextNode(); |
| continue; |
| } |
| |
| if (IsTargetDead(instruction)) { |
| instruction = context()->KillInst(instruction); |
| modified = true; |
| } else { |
| instruction = instruction->NextNode(); |
| } |
| } |
| |
| instruction = &*get_module()->annotation_begin(); |
| while (instruction) { |
| if (instruction->opcode() != SpvOpDecorate && |
| instruction->opcode() != SpvOpDecorateId) { |
| instruction = instruction->NextNode(); |
| continue; |
| } |
| |
| if (IsTargetDead(instruction)) { |
| instruction = context()->KillInst(instruction); |
| modified = true; |
| } else { |
| instruction = instruction->NextNode(); |
| } |
| } |
| |
| // Kill dead instructions and remember dead blocks |
| for (auto bi = structuredOrder.begin(); bi != structuredOrder.end();) { |
| uint32_t mergeBlockId = 0; |
| (*bi)->ForEachInst([this, &modified, &mergeBlockId](ir::Instruction* inst) { |
| if (dead_insts_.find(inst) == dead_insts_.end()) return; |
| // If dead instruction is selection merge, remember merge block |
| // for new branch at end of block |
| if (inst->opcode() == SpvOpSelectionMerge || |
| inst->opcode() == SpvOpLoopMerge) |
| mergeBlockId = inst->GetSingleWordInOperand(0); |
| context()->KillInst(inst); |
| modified = true; |
| }); |
| // If a structured if or loop was deleted, add a branch to its merge |
| // block, and traverse to the merge block and continue processing there. |
| // We know the block still exists because the label is not deleted. |
| if (mergeBlockId != 0) { |
| AddBranch(mergeBlockId, *bi); |
| for (++bi; (*bi)->id() != mergeBlockId; ++bi) { |
| } |
| } else { |
| ++bi; |
| } |
| } |
| // Cleanup all CFG including all unreachable blocks |
| CFGCleanup(func); |
| |
| return modified; |
| } |
| |
| void AggressiveDCEPass::Initialize(ir::IRContext* c) { |
| InitializeProcessing(c); |
| |
| // Clear collections |
| worklist_ = std::queue<ir::Instruction*>{}; |
| live_insts_.clear(); |
| live_local_vars_.clear(); |
| dead_insts_.clear(); |
| |
| // Initialize extensions whitelist |
| InitExtensions(); |
| } |
| |
| Pass::Status AggressiveDCEPass::ProcessImpl() { |
| // Current functionality assumes shader capability |
| // TODO(greg-lunarg): Handle additional capabilities |
| if (!context()->get_feature_mgr()->HasCapability(SpvCapabilityShader)) |
| return Status::SuccessWithoutChange; |
| // Current functionality assumes relaxed logical addressing (see |
| // instruction.h) |
| // TODO(greg-lunarg): Handle non-logical addressing |
| if (context()->get_feature_mgr()->HasCapability(SpvCapabilityAddresses)) |
| return Status::SuccessWithoutChange; |
| // If any extensions in the module are not explicitly supported, |
| // return unmodified. |
| if (!AllExtensionsSupported()) return Status::SuccessWithoutChange; |
| // Process all entry point functions |
| ProcessFunction pfn = [this](ir::Function* fp) { return AggressiveDCE(fp); }; |
| bool modified = ProcessEntryPointCallTree(pfn, get_module()); |
| return modified ? Status::SuccessWithChange : Status::SuccessWithoutChange; |
| } |
| |
| AggressiveDCEPass::AggressiveDCEPass() {} |
| |
| Pass::Status AggressiveDCEPass::Process(ir::IRContext* c) { |
| Initialize(c); |
| return ProcessImpl(); |
| } |
| |
| void AggressiveDCEPass::InitExtensions() { |
| extensions_whitelist_.clear(); |
| extensions_whitelist_.insert({ |
| "SPV_AMD_shader_explicit_vertex_parameter", |
| "SPV_AMD_shader_trinary_minmax", |
| "SPV_AMD_gcn_shader", |
| "SPV_KHR_shader_ballot", |
| "SPV_AMD_shader_ballot", |
| "SPV_AMD_gpu_shader_half_float", |
| "SPV_KHR_shader_draw_parameters", |
| "SPV_KHR_subgroup_vote", |
| "SPV_KHR_16bit_storage", |
| "SPV_KHR_device_group", |
| "SPV_KHR_multiview", |
| "SPV_NVX_multiview_per_view_attributes", |
| "SPV_NV_viewport_array2", |
| "SPV_NV_stereo_view_rendering", |
| "SPV_NV_sample_mask_override_coverage", |
| "SPV_NV_geometry_shader_passthrough", |
| "SPV_AMD_texture_gather_bias_lod", |
| "SPV_KHR_storage_buffer_storage_class", |
| // SPV_KHR_variable_pointers |
| // Currently do not support extended pointer expressions |
| "SPV_AMD_gpu_shader_int16", |
| "SPV_KHR_post_depth_coverage", |
| "SPV_KHR_shader_atomic_counter_ops", |
| }); |
| } |
| |
| } // namespace opt |
| } // namespace spvtools |
